This invention relates generally to excavation of soil, and more particularly to pneumatic excavation.
Tools for locating and uncovering buried utilities and other buried objects, such as tree roots etc., safely and effectively, using supersonic air jets powered by commercial air compressors, and using one or more supersonic excavation nozzles, have been used in recent years. Supersonic is defined as any speed over the speed of sound (Mach1), which is approximately 761 mph. Also, air tools for vacuuming the soil from the excavation site, such soil having been previously crumbled by a supersonic air digger or other means, have also been in common use. Some of these pneumatic excavation tools are handheld for manipulation by an individual user or users. In other instances the tools are very large and heavy and must therefore be mounted on a vehicle such as a truck or tractor, which also carries the air pressure source for the digging and usually a separate mechanical source for the vacuum evacuation.
Two such prior art structures are illustrated in U.S. Pat. Nos. 5,212,891 and 5,361,855, which use a single air source with two valve controls, one valve to control the supersonic air digging or excavation nozzle, and a second valve to control a non-supersonic air nozzle to assist in evacuation of the crumbled material. Prior art reference U.S. Pat. No. 4,991,321, utilizes a single air source under the control of a single valve to supply air under pressure to the supersonic excavation nozzle, and, in parallel, a second non-supersonic nozzle with a second control valve to carry excavate out of the excavation.
A fourth prior art reference, U.S. Pat. No. 5,140,759, uses a single air source under the control of a single valve to supply non-supersonic air excavation nozzles, and, in parallel thereto, non-supersonic nozzles to vacuum excavate out of the excavation. The innovation of this prior art reference relates to the use of a manual valve of multiple positions that supplies the two nozzle sets with air in various degrees, alternatively or simultaneously in variable amounts.
There still exists a great need for new, unique pneumatic excavation devices of better performance and greater capabilities, particularly for tunneling in differing applications and degrees of difficulty and for excavating under pavements, such as sidewalks, driveways and roads.